Method of hot forming of hollow mushroom type metallic parts

ABSTRACT

This invention relates to a method of hot forming from a blank pipe hollow mushroom type metallic parts having a hollow stem and a cap portion whose outer diameter is far larger than that of the blank pipe. By using a thin-walled pipe whose size corresponds to that of the hollow stem processing of the hollow stem can be omitted or minimized. More particularly, it relates to a method of hot forming hollow valves for engines or parts having a cap portion and hollow stem, the outer diameter of said cap portion being more than two or three times as large as that of the stem portion, by using a thin-walled pipe having a ratio between its outer diameter and its wall thickness of more than 3.5.

United States Patent [191 Iwata et al.

[ METHOD OF HOT FORMING OF HOLLOW MUSHROOM TYPE METALLIC PARTSInventors: Tokushige lwata; Nobuyoshi Hojyo;

Tokushi Ando; Masao Miwa, all of Kyoto, Japan Filed: June 1, 1972 Appl.No.: 258,854

[30] Foreign Application Priority Data June 10, 1971 Japan 46-49548References Cited UNITED STATES PATENTS 6/1930 Thompson et al. 29/156.711/1948 Bartlett et a1 29/156.7

[ Feb. 26, 1974 1,991,199 2/1935 Eisele 72/368 2,053,975 9/1936 Spatta72/367 FOREIGN PATENTS OR APPLICATIONS 679,331 2/1964 Canada 72/3774,511,421 4/1970 Japan 72/342 Primary ExaminerLowell A. Larson Attorney,Agent, or Firm-Toren & McGeady [5 7] ABSTRACT This invention relates toa method of hot forming from a blank pipe hollow mushroom type metallicparts having a hollow stem and a cap portion whose outer diameter is farlarger than that of the blank pipe. By using a thin-walled pipe whosesize corresponds to that of the hollow stem processing of the hollowstem can be omitted or minimized. More particularly, it relates to amethod of hot forming hollow valves for engines or parts having a capportion and hollow stem, the outer diameter of said cap portion beingmore than two or three times as large as that of the stem portion, byusing a thin-walled pipe having a ratio between its outer diameter andits wall thickness of more than 3.5.

8 Claims, 9 Drawing Figures PATENTEDFEBZGW 3.793.873

' sum a 052 'F|G.'4 FIG.5

PRESSURE (.Kg/cm (OIL PRESSURE v o 01 METHOD OF HOT FORMING OF HOLLOWMUSHROOM TYPE METALLIC PARTS This invention relates to a method offorming hollow parts of a thin walled configuration such as hollowvalves for engines. More particularly, it relates to a method of forminghollow mushroom type metallic parts having a projected cap portion whoseouter diameter is larger than that of the stem.

Conventional hot forming methods for forming hollow mushroom typemetallic parts are accomplished by means of an upsetting press orextruding press by utilizing solid steel bars. The solid bars arehollowed out before hand or are made hollow simultaneously withextrusion pressing.

The former method is disadvantageous in that the life of the cuttingtool used is short and the required number of man hours is great. Thelatter method has disadvantages that the wall thickness of the hollowportion or the accuracy of the size of the bent portion is not uniformand the life of the dies is short. In the case of hollow valves, hotdraw forging or the hot forming method according to the specification ofUS. Pat. No. 3,358,350 has been conventionally used. These methods areconsidered uneconomical because of the increased number of man hoursinvolved in the process.

The object of this invention is to eliminate the abovementioneddrawbacks and to provide a hot forming method which is applicable to theproduction not only of entirely hollow valves but also of hollow bodyvalves for engines, and the invention can easily and economically beused to manufacture hollow mushroom type metallic parts wherein havingthe stem is of a shape similar to that of a thin-walled pipe materialused in forming the valve. In order to achieve this object, the methodembodying this invention for hot upset forging of hollow mushroom typemetallic parts from thinwalled pipe material resides in the combinationof an upsetting process to be accomplished after the pipe end to beupset is bent outwardly to be buckled before the upsetting process oralternatively, at the early stage of said process by bringing said endportion into contact with an upsetting anvil, and includes a subsequentpressing process in which press dies provided with allowances forremoving excess metal of said buckled portion of pipe at least at theplace corresponding to the top of the cap portion of the mushroom typeparts are utilized.

Other objects and advantages of this invention will be apparent from thefollowing description which should be read in conjunction with theaccompanying drawings.

In the accompanying drawings:

FIGS. la-b illustrates an embodiment of the forming method of hollowmushroom type metallic parts according to this invention in which theprocess of upsetting a hollow valve from a pipe material is shown;

FIGS. 2a-b and 3a-b are cross-sectional views of forming conditions of ahollow valve;

FIG. 4 shows an example of an electrode anvil provided with a projectionwhich can be used at the time of upsetting according to the methodembodying this invention;

FIG. 5 shows an example of an upper die provided with a projection whichcan be used at the time of press forging according to the methodembodying this invention; and

FIG. 6 is a graph illustrating the processing condition in a case wherethe pipe shown in FIG. I is to be upset after the pipe end is bent to bebuckled at the early stage of upsetting process so that said end isbrought into contact with an upsetting anvil.

FIG. 1(a) illustrates the set-up condition of a blank material 1 in acase where a direct current electric upsetter is employed. A pipematerial 1 is located between a fixed electrode anvil 2 and a pusher 4.The pipe material I placed between a clamped electrode 3 and theelectrode anvil 2 is subjected to resistance heating. The pipe material1 is upset while the clamped electrode 3 is being caused to slide bymeans of the pusher 4. Thus, upsetting is accomplished in the samemanner as in upsetting by means of conventional upsetters.

According to the method of this invention, first of all the pipe isoutwardly bent to cause buckling at the end y thereof to be brought intocontact with the electrode anvil 2 before the start of upsetting orafter the start of upsetting as shown by the dotted line (diameter Do)in FIG. 1, or the pipe is bent especially by the pressure exerted at theearly stage of upsetting while gradually increasing the pressureapplication of the speed of pusher 4 as shown, for example, in FIG. 6 sothat the pipe is upset while it is being buckled. After that, the pipe 1is processed by increasing the pressure gradually at the later stage ofthe upsetting process. In this way, upsetting sufficient to insuresubsequent projection of a cap portion of mushroom shape can be obtainedas shown in FIG. 1(b).

The buckling diameter D0 of the pipe end effected by bending isdetermined by considering several parameters including the setting ofthe interelectrode space, the upsetting speed under pressure, pipeheating temperature and pipe material. In the case of steel pipe, thediameter Do should be preferably about 1.5 2 times the outer diameter dof the pipe.

Referring now to FIG. 1(b), if the pipe outer diameter 11 is 8 10 mm andthe wall thickness 1 is in the range of 1.5 2.5 mm, an upsettingthickness T which is about 5 6 times the wall thickness t can be easilyobtained.

When a pipe having a think wall is upset as it is according to theconventional upsetting process without performing the operationembodying this invention, the outer and inner circumferences of the pipewill be deformed in the so-called snake shape, and therefore mushroomtype parts of required configuration cannot be obtained. Even if theratio d/t is less than about 3.5, the method according to this inventionis preferable for obtaining a greater upsetting amount. When the ratiod/t exceeds 3.5 4.0, flawless mushroom type parts of satisfactoryconfiguration can be obtained according to the method embodying thisinvention.

After the upsetting process as illustrated in FIG. 1(b) is completed,die forging (by means of a press) as shown in FIGS. 2(a), (b) or 3(a),(b) is carried out. In this case, the bent portion shown in FIG. 1(b)remains as a striking mark e as shown in FIG. 2 or 4. Allowances shouldbe made in the size of dies (upper or lower die) so that said strikingmark e can be removed at the time of completion.

FIGS. 2(a) and (b) illustrate a hollow mushroom type part having ahollow cap. FIG. 2(a) shows an example in which allowances for removalof striking mark e are made in the lower dies of the press. FIG. 2(b)shows an example in which allowances for removal of striking mark e aremade in the upper die. The striking mark e is removed along the removalline 1: at the time of completion.

FIGS. 3(a) and (b) illustrate examples in which the cap portion is madesolid by increasing the upsetting amount shown in FIG. 1(b) than in theexamples of FIGS. 2(a) and (b). These are embodiments for producing theso-called hollow body valve.

The parts shown in FIGS. 3(a) and (b) are produced by the same processas in FIGS. 2(a) and (b) which correspond to FIGS. 3(a) and (b),respectively. In the parts shown in FIGS. 3(a) and (b), the axiallyjoined portion remains in the center of the cap portion. This is amechanically joined condition remaining as a narrow line along thecenter line as a result of compression of the pipe wall toward the axisat the time of forging. Depending on the purpose of use, such parts canbe used as they are. If the pipe inner surface is subjected to highlyfusible metal plating or has applied thereto a flux such as borax asappropriate, it is possible to strengthen adhesion of the axially joinedportion c.

Accordingly, in case of producing, for example, hollow suction valves inwhich reduction in weight is the aim, it is not necessary to enclose,for example, sodium after the above-mentioned processes are completed.The valves having the axially joined portion c in the mechanicallyjoined condition can be used as they are.

When a high degree of adhesion is required by admitting high pressuregas, fluid or the like into the hollow portion, the axially joinedportion 0 may be welded by, for example, electron-beam welding, laserwelding or the like as appropriate.

In order to ensure reliable forming of the lateral side of said hollowportion in forming parts with a hollow cap portion as shown in FIG. 2,upsetting according to the method of this invention may be accomplishedby using the electrode anvil 2 having an appropriately taperedprojection f which can be inserted to extend well into the pipematerial. Or, a similar projection g may be provided on the press upperdie which is used at the time of the pressing process as shown in FIG.5.

In case of parts having either a hollow cap or a hollow stem, the lengthof the heating time shown in, for example, FIG. 1 and the forging ratioT/t should be appropriately selected in accordance with the requiredshape.

The above-described embodiments utilize a direct current electricheating method. However, other rapid heating methods such ashigh-frequency induction, plasma or flame heating may be employed. It isneedless to say that the forgings obtained by the forming method asshown in FIG. 2 or 3 are processed into finished products throughsubsequent heat treatment or grinding of the inner and outer surfaces.

We claim:

1. A method for manufacturing hollow-mushroomshaped engine valves fromhollow blanks of thin walled pipe material utilizing hot upset forgingtechniques to form said valves with a mushroom shaped top portion and alower stem portion, comprising the steps of initially buckling one endof said pipe material to effect bending of the wall of said pipematerial at said buckled end outwardly from the hollow interior thereof,upsetting said buckled end by bringing said end into contact with anupsetting anvil thereby to form said end into a mushroom shaped capportion, and pressing said metallic parts in press dies and removingtherefrom during said pressing step excess material formations caused bysaid buckling step at portions of said metallic parts along the top ofsaid mushroom-shaped cap portion.

2. The method according to claim 1 wherein the outer diameter of saidpipe is 3.5-4.0 times the wall thickness of the pipe.

3. The method according to claim 1 wherein said hollow engine valves areheated by electrical resistance heating.

4. The method according to claim 1 wherein said buckling step isperformed in the initial stages of said upsetting step as part of saidupsetting step.

5. The method according to claim 4 wherein said upsetting step isperformed by abutting said pipe material blank against an upsettinganvil and applying pressure thereto, with a lower pressure being appliedin the early stages of said upsetting step to perform said buckling stepand with said pressure application being subsequently increased duringthe latter stages to complete said upsetting step.

6. The method according to claim I wherein striking marks are formed insaid buckled end during said buckling step, and wherein said strikingmarks are removed during said pressing step with the removal of saidexcess material formations.

7. The method according to claim 1 wherein said metalic parts are formedwith a hollow stem and a closed solid mushroom shaped cap portion byincreasing the amount of material which is upset in said upsetting stepthereby to form said cap portion as a closed solid mushroom shape.

8. The method according to claim I wherein an appropriately shaped dieprojection is provided for insertion extending well into said pipeblank.

1. A method for manufacturing hollow-mushroom-shaped engine valves fromhollow blanks of thin walled pipe material utilizing hot upset forgingtechniques to form said valves with a mushroom shaped top portion and alower stem portion, comprising the steps of initially buckling one endof said pipe material to effect bending of the wall of said pipematerial at said buckled end outwardly from the hollow interior thereof,upsetting said buckled end by bringing said end into contact with anupsetting anvil thereby to form said end into a mushroom shaped capportion, and pressing said metallic parts in press dies and removingtherefrom During said pressing step excess material formations caused bysaid buckling step at portions of said metallic parts along the top ofsaid mushroom-shaped cap portion.
 2. The method according to claim 1wherein the outer diameter of said pipe is 3.5-4.0 times the wallthickness of the pipe.
 3. The method according to claim 1 wherein saidhollow engine valves are heated by electrical resistance heating.
 4. Themethod according to claim 1 wherein said buckling step is performed inthe initial stages of said upsetting step as part of said upsettingstep.
 5. The method according to claim 4 wherein said upsetting step isperformed by abutting said pipe material blank against an upsettinganvil and applying pressure thereto, with a lower pressure being appliedin the early stages of said upsetting step to perform said buckling stepand with said pressure application being subsequently increased duringthe latter stages to complete said upsetting step.
 6. The methodaccording to claim 1 wherein striking marks are formed in said buckledend during said buckling step, and wherein said striking marks areremoved during said pressing step with the removal of said excessmaterial formations.
 7. The method according to claim 1 wherein saidmetalic parts are formed with a hollow stem and a closed solid mushroomshaped cap portion by increasing the amount of material which is upsetin said upsetting step thereby to form said cap portion as a closedsolid mushroom shape.
 8. The method according to claim 1 wherein anappropriately shaped die projection is provided for insertion extendingwell into said pipe blank.